Method of joining the edge portions of two sheets

ABSTRACT

The edge portion of each sheet is provided with a rectangular pattern of ribs, and the sheets are placed together with one edge portion extending beyond the other. The former is folded back over the latter so that intersecting portions of the ribs are compressed to firmly lock the sheets together.

O United States Patent 1191 1111 3,861,339 Aida et al. Jan. 21, 1975 METHOD OF JOINING THE EDGE 697,956 4/1902 Thompson 220/76 PORTIONS or TWO SHEETS 74911 16 1/ 1904 1,796,114 3/1931 Meadowcroft 113/116 D Inventors: Hiroyuki Aida; Norihiro Tsuneishi; 1,808,561 6/1931 Ledwinka 113/116 c Hideo Takizawa; Yoshiyuki 3,680,910 8/1972 Stanner 29/513 X Miyabayashi, all of Tokyo, Japan 3,719,986 3/1973 Ardolino et al 29/521 X [73] Assignee: Nissan Motor Company, Ltd.,

Yokohama, Japan Primary ExammerC. W. Lanham 1 Flledi J 1974 Assistant Examiner-Victor A. DiPalma Attorne A nt or FirmRobert E. Burns" .I 4 Y 8 1 [211 NO 437 71 Emmanuel .l. Lobato; Bruce L. Adams [30] Foreign Application Priority Data Jan. 31, 1973 Japan 48-13525[U] 57 ABSTRACT [52] U.S. Cl 113/116 C, 29/505, 29/521,

113/1 N 51 1111. C1 B21d 51/00 The edge Portion of each Sheet is Provided with a rect- [58] Field Of Search 29/463, 462, 509, 512, angular pattern of ribs, and the Sheets are placed 5 3 5 505; 13 C, 11 p 11 R, gether with one edge portion extending beyond the 1 N, 11 R other. The former is folded back over the latter so that intersecting portions of the ribs are compressed to [56] References Cited firmly lock the sheets together.

UNITED STATES PATENTS 518,767 4/ 1894 Plecker 29/505 X 2 Claims, 5 Drawing Figures METHOD OF JOINING THE EDGE PORTIONS OF TWO SHEETS The present invention relates to a method of joining the edge portions of two sheets without using supplementary means such as mechanical fasteners, metal-tometal adhesives or welding techniques.

Sheet metal members are often joined by a lock joint which is produced by folding an edge portion of one member back over an edge portion of the other member. Examples of combinations of such sheet metal members are, in an automotive vehicle, inner and outer wall members of a door structure, a front fender and a front fender supporting hood, and an outer wall member and an associated reinforcing member of a trunk structure.

To assemble these sheet metal members by folding as mentioned above, it is a common practice to have one of the sheet metal members superimposed on the other and fold an edge portion of the former back over on edge portion of the latter so that the edge portions of the two members are in close contact with each other. In order that two sheet metal members combined in this manner are prevented from being displaced relative to each other from their initially fixed positions, it is important that the sheet metal member held by the folded sheet metal member be sufficiently tightly held by the folded member so that no gap exists between the edge of the edge portion of the former and the folded over end of the latter. Since, however, the dimensional accuracy usually varies from one sheet metal member to another where the sheet metal members are manufactured on a large-scale commercial basis, and for the purpose of achieving satisfactory productivity in the assembly of sheet metal members as in the automotive industry, it is practically impossible to achieve a gapfree fit between sheet metal members which are combined by the prior art folding process. To prevent relative displacement between joined sheet metal members, the sheet metal members may be subjected to additional processing such as, for example, spot-welding or bonding with a metal-to-metal adhesive during the assembly operation to provide reinforcement for the lock joint produced in the assembled structure. If, however, the sheet metal members are spot-welded when they are being joined together, the members tend to be distorted, and additional operations and equipment are necessitated to remedy the distortion of the members combined; especially with members which are oriented outwardly in working positions in a final product such as an automotive vehicle. To constantly achieve accuracy in spot-welding operations of a great of workpieces, sustained maintenance and servicing efforts are indispensable of jigs used for the spot-welding operations. If, on the other hand. a metal-to-metal adhesive is used to reinforce the lock joint between the sheet metal members, it becomes difficult to maintain the initially fixed relative positions of the joined members throughout the succeeding steps of the assembly operation during which the adhesive applied to the members remains wet. Sheet metal members joined together using a metal-to-metal adhesive are thus still subject to relative displacement until they are painted and baked during the final stages of the assembly operation. The present invention contemplates elimination of all the above mentioned drawbacks which are inherent in joining edge portions of two sheet metal members by a prior art folding process.

It is accordingly an important object of the present invention to provide a method of tightly joining edge portions of two sheets without supplementary processing such as chemical bonding, welding or the use of supplementary fasteners such as bolts or rivets.

The above and other objects features and advantages of the invention will become clear from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross sectional view of two sheet metal members whose edges are joined by a prior art folding method;

FIG. 2 is a perspective view of a preferred method of joining the edges of two sheets according to the invention; and

FIG. 3 is a cross sectional view of sheets joined by the method of FIG. 2, and FIGS. 4A and 4B are plan views of a door assembly joined by a method ofthe invention.

FIGS. 4A and 4B show an example of practical structural members joined by a method of the invention. An automobile door assembly includes a door 6 and a door inner panel 8 joined to the door 6. FIG. 4A shows the outside of the door 6 and FIG. 4B shows the outside of the door 6 and the inner panel 8. The methods of the invention relate to joining the inner panel 8 to the door 6 by folding an edge portion 6a of the door 6 back over the peripheral edge of the inner panel 8.

FIGS. 4A and 4B are exemplary only, and the invention is not limited to automotive doors or other automotive structures. FIGS. 1 to 3 can be considered as illustrating methods of joining the inner panel 8 to the door 6 within a portion surrounded by a broken circle S.

As illustrated in FIG. 1, edge portions of sheet metal members 10 and 12 are joined by a conventional folding method so that an edge portion 10a of the sheet metal member 10 is folded back over an edge portion 12a of the other sheet metal member 12 so that the latter is tightly gripped by the former. For the reasons above, a gap 14 is inevitably produced between the inner surface of the folded end of the sheet metal member 10 and the edge of the edge portion 12a of the sheet metal member 12. The goal of the present invention is to join the edges of the sheet metal members 10 and 12 by a sufficiently tight and rigid lock joint which can be produced without the use of mechanical fasteners, metal-to-metal adhesives or spot-welding.

FIG. 2 illustrates a method of joining two sheets 16 and 20 at their edges according to the invention, which have edge portions 16a and 20a respectively. Ribs l8 and secondary ribs 18' are formed on a surface of the edge portion 16a, and ribs 22 and secondary ribs 22' are formed on a surface of the edge portion 20a. The ribs and secondary ribs of each sheet are generally parallel to one another, and the secondary ribs 18' and 22' are generally perpendicular to the respective ribs 18 and 22. The ribs 18 and 22 are shown as being parallel to the edges of the sheets 16 and 20 respectively and the secondary ribs 18 and 22' perpendicular thereto, but such need not be the case.

The sheets are then placed together with the edge portion 20a extending beyond the edge portion 16a, and the edge portion 20a is tightly folded back over the edge portion 16a in the direction of an arrow A as shown. The sheets 16 and 20 are placed together using any known method of alignment so that when the edge portion a is folded back over the edge portion 16a, the surfaces of the sheets having the ribs and secondary ribs formed thereon engage with each other as shown in FIG. 3, and intersecting portions of ribs and secondary ribs are compressed to prevent relative movement between the sheets.

As shown in FIG. 3, when the edge portion 20a is folded back over the edge portion 16a, the alignment is such that the ribs 18 are spaced from the ribs 22. This is to avoid a weak joint due to engagement of the ribs 18 and 22 along their entire length. A similar relationship exists between the secondary ribs 18' and 22'. If the alignment is such that the ribs 18 and 22 are parallel to each other and the secondary ribs 18 and 22' are thus also parallel to each other upon folding, intersecting portions will be formed between the ribs 18 and the secondary ribs 22, and between the ribs 22 and the secondary ribs 18' as points of a regular rectangular matrix. The material of the ribs and secondary ribs in these intersecting portions will be compressed to provide a tight lock joint between the sheets 16 and 20 in spite of the gap 14 between a folded end 20b of the sheet 20 and the gripped edge of the edge portion 16a.

Although the ribs and secondary ribs may be oriented in a mutually rectangular pattern upon folding as described above, such need not be the case within the scope of the invention. The edge portion 20a may be folded over the edge portion 16a in such a manner that an angle other than 90 is provided between the ribs of one sheet and the secondary ribs of the other sheet. In this case, the ribs 18 will intersect both the secondary ribs 22' and the ribs 22, and the ribs 22 will intersect both the secondary ribs 18' and the ribs 18.

Another option within the scope of the invention is to eliminate either the ribs of both sheets or the secondary ribs of both sheets. It is more desirable to eliminate the secondary ribs in order to prevent relative movement between the sheets perpendicular to the end 20b due to the existence of the gap 14, but alternative elimination of the ribs is also within the scope of the invention. In either case, the ribs or secondary ribs as provided may either be oriented parallel to each other upon folding and therefore not intersect, or be nonparallel to each other and intersect as in the method illustrated. In the former case, the ribs of one sheet are spaced entirely from the ribs of the other sheet, and in the latter case, the ribs of one sheet are spaced at portions thereof from the ribs of the other sheet.

Although the invention provides a tight lock joint without supplementary welding, adhesives. mechanical fasteners, etc., as is clear from the description. any of these methods may be employed to increase the strength of the lock joint provided by a method of the invention if desired.

What is claimed is:

l. A method of joining two sheets at their edges.

comprising the steps of:

a. forming a plurality of substantially parallel ribs on a surface of the edge portion of one sheet;

b. forming a plurality of substantially parallel ribs on a surface of the edge portion of the other sheet;

c. placing the sheets together with one of the edge portions extending beyond the other edge portion; and

d. tightly folding the edge portion extending beyond the other edge portion back over the other edge portion so that the surfaces of the sheets having the ribs formed thereon engage with each other and the ribs of the one sheet are spaced at least at portions thereof from the ribs of the other sheet.

2. A method as claimed in claim 1, further comprising the steps of;

e. forming a plurality of substantially parallel secondary ribs on the surface of the edge portion of the one sheet substantially perpendicular to the ribs thereof; and

f. forming a plurality of substantially parallel secondary ribs on the surface of the edge portion of the other sheet substantially perpendicular to the ribs thereof;

prior to performing step c;

and in which the secondary ribs of the two sheets are spaced at least at portions thereof from each other while performing step d;

intersecting portions of ribs and secondary ribs being compressed during performance of step d to prevent relative movement between the sheets. 

1. A method of joining two sheets at their edges, comprising the steps of: a. forming a plurality of substantially parallel ribs on a surface of the edge portion of one sheet; b. forming a plurality of substantially parallel ribs on a surface of the edge portion of the other sheet; c. placing the sheets together with one of the edge portions extending beyond the other edge portion; and d. tightly folding the edge portion extending beyond the other edge portion back over the other edge portion so that the surfaces of the sheets having the ribs formed thereon engage with each other and the ribs of the one sheet are spaced at least at portions thereof from the ribs of the other sheet.
 2. A method as claimed in claim 1, further comprising the steps of; e. forming a plurality of substantially parallel secondary ribs on the surface of the edge portion of the one sheet substantially perpendicular to the ribs thereof; and f. forming a plurality of substantially parallel secondary ribs on the surface of the edge portion of the other sheet substantially perpendicular to the ribs thereof; prior to performing step c; and in which the secondary ribs of the two sheets are spaced at least at portions thereof from each other while performing step d; intersecting portions of ribs and secondary ribs being compressed during performance of step d to prevent relative movement between the sheets. 